1. Field of the Invention
This invention relates to a novel process for the oil extraction from oil sand by using cyclodextrin.
2. Description of the Prior Art
Processes for the oil extraction from sand oil known in the art include a process for the oil extraction in situ comprising introducing steam at high temperature and high pressure into a layer containing oil sand, that is, a steam separation process, and a process for separating oil from open-air oil sand by using alkaline water at an elevated temperature. However, these processes have an economical disadvantage since they need a great amount of energy. Recently, a new oil-extraction process has been proposed which utilizes an inclusion capability of cyclodextrin and comprises including oil molecule contained in oil sand within a cavity of cyclodextrin molecule and then separating the inclusion compound to collect oil (see Japanese Patent Disclosure No. 133484/1980). This process is economically better than the steam separation process described above and comprises forming an inclusion compound of oil and cyclodextrin, separating the resulting, water-insoluble inclusion compound by any suitable technique such as centrifugation, and then introducing the separated inclusion compound into hot water or subjecting it to steam distillation to collect oil. Thus, the new process requires a troublesome operation and takes a relatively long time. The oil extraction yield of this process is not good (generally about 60%) due to the troublesome operation. As described above, the process using an inclusion compound mentioned above is not suitable for an industrial production in view of yield, time and cost.
The inventors of the present invention have paid attention to a special physical property of cyclodextrin, that is, the fact that cyclodextrin has surface activity and also accelerates separation between oil and sand contained in oil sand, and studied a process of oil extraction from oil sand by using cyclodextrin. The inventors have found that the oil extraction from oil sand may easily and effectively be conducted by mixing oil sand, cyclodextrin and water with one another to prepare a suspension and leaving the suspension to stand or centrifuging it to separate an oil layer. The present invention has been accomplished based on the discovery mentioned above.